Glime, J. M. 2019. Tropics: Wet and Dry Habitats. Chapt. 8-11. In: Glime, J. M. Bryophyte Ecology. Volume 4. Habitat and Role. 8-11-1 Ebook sponsored by Michigan Technological University and the International Association of Bryologists. Last updated 22 July 2020 and available at <http://digitalcommons.mtu.edu/bryophyte-ecology4/>. CHAPTER 8-11 TROPICS: HYDRIC AND XERIC HABITATS TABLE OF CONTENTS Inundated Forests ................................................................................................................................................................. 8-11-2 Várzea and Igapó Forests ............................................................................................................................................. 8-11-2 Floodplains and Mangrove Forests .............................................................................................................................. 8-11-4 Pirizal ........................................................................................................................................................................... 8-11-8 Peatlands .............................................................................................................................................................................. 8-11-8 Aquatic ............................................................................................................................................................................... 8-11-11 Rheophytes ................................................................................................................................................................. 8-11-12 Lakes .......................................................................................................................................................................... 8-11-16 Seepage Areas .................................................................................................................................................................... 8-11-20 Xeric Habitats .................................................................................................................................................................... 8-11-21 Savannahs .................................................................................................................................................................. 8-11-24 Succession .......................................................................................................................................................... 8-11-25 Life Cycle Strategies .......................................................................................................................................... 8-11-26 Tropical Deserts ......................................................................................................................................................... 8-11-27 Summary ............................................................................................................................................................................ 8-11-31 Acknowledgments ............................................................................................................................................................. 8-11-31 Literature Cited .................................................................................................................................................................. 8-11-31 8-11-2 Chapter 8-11: Tropics: Wet and Dry Habitats CHAPTER 8-11 TROPICS: HYDRIC AND XERIC HABITATS Figure 1. Várzea in Brazil. Photo by D. N. Santos, through Creative Commons. gives the water a golden appearance (Figure 4) (Pires & Inundated Forests Prance 1985). In flood season, the igapó trees are flooded so that their trunks are completely submerged (Figure 5), The classification of inundated forests has been permitting one to canoe through the canopy (Figure 6). inconsistent even by botanists, particularly in different regions (Prance 1980), making descriptions of the vegetation based on literature difficult and confusing. Prance divided these forests into periodically inundated (seasonal várzea, seasonal igapó, mangrove, tidal várzea, flood plain forest) and permanently waterlogged (permanent white water swamp forest, permanent igapó). Inundated forests are forests that are constantly or periodically in water and include the igapós (Figure 2- Figure 3) and várzeas (Figure 1, Figure 7) (Pires & Prance 1985). These flood forests cover 2% or more of Brazilian Amazonia, excluding the rivers themselves. For example, the palm Astrocaryum jauari is, in various places, flooded 30-340 daya a year (Piedale et al. 2005, 2006). The igapós are black and clearwater areas, whereas the várzeas are Figure 2. Diagram of igapó showing water level fluctuation muddy waters. In the black and clearwater areas, the igapó for a mound of trees. Modified from Piedade et al. 2006. Chapter 8-11: Tropics: Wet and Dry Habitats 8-11-3 Figure 3. Flooded igapó forest in Black River of Figure 6. Canoeing through canopy of flooded igapó forest Anavilhana, Brazil, in 2014. Photo courtesy of Tatiany Oliveira in Black River of Anavilhana, Brazil, in 2014. Photo courtesy of da Silva. Tatiany Oliveira da Silva. Várzea and Igapó Forests The classification of Amazonian floodplains is based on water and vegetation types (Ferreira et al. 2005, 2013). The igapó (Figure 8) and várzea (Figure 1, Figure 7) are the most common of these. The várzea is a seasonally whitewater-flooded forest growing along rivers in the Amazon. The igapó forests are seasonally inundated with freshwater and typically occur along the lower reaches of rivers and around freshwater lakes, whereas the permanent igapó forest is in water year-round, but with fluctuating water levels. Using 100 plots, each of 20 x 20 m, within 4 hectares, Ferreira and coworkers (2013) identified all trees and lianas greater than 10 cm diameter at breast height. They identified a total of 97 species, with 75 in igapó and 48 in várzea forests. Only 26 species occurred in both forests, Figure 4. Golden water in flooded igapó forest in Black indicating that these are distinct forests. The várzea forests River of Novo Airão, state of Amazonas, Brazil, in 2014. Photo have more soil nutrients, more light availability, and courtesy of Tatiany Oliveira da Silva. greater natural disturbance, perhaps helping to explain the plant diversity differences. Figure 5. Flooded igapó forest in Black River of Anavilhana, Brazil, in 2014. Photo courtesy of Tatiany Oliveira Figure 7. Várzea forest, Marajó, Brazil. Photo by Dayse da Silva. Ferreira, through Creative Commons. 8-11-4 Chapter 8-11: Tropics: Wet and Dry Habitats Figure 10. Reproduction of bryophytes in inundated forests. Numbers refer to number of species. Modified from Cerqueira et al. 2016. Lopes et al. (2016) compared the bryophyte communities as they relate to degrees of flooding in the igapó and várzea. They sampled eighteen transects each in the igapó and várzea forests of São Domingos do Capim, Pará State, Brazil. As in many rainforest studies, they found that the leafy liverwort family Lejeuneaceae (Figure 28) was the predominant family, with 63 species. Among the mosses, the Calymperaceae (Figure 11, Figure 30) had Figure 8. Igapó in Brazil. Photo by Lisa Cyr, through the most species, with 8 species. In total, they reported 118 Creative Commons. bryophyte species, 82 liverworts and 37 mosses. Live bark was the most colonized substrate, with 45 species exclusive Cerqueira et al. (2017) studied the epiphytic to it, but 101 species in total on bark. Decomposing bark bryophytes on Virola surinamensis (baboonwood; Figure followed, with 66 species, 16 of which were exclusive to it. 9) in igapó (Figure 8) and várzea (Figure 7) forests in the Caxiuanã National Forest. They found a greater richness in Floodplains and Mangrove Forests the igapó forest (44 species) compared to that of the várzea forest (38 species) (Figure 10). Furthermore, the Mangrove forests and floodplains are subject to composition of the bryophyte communities differed inundation by salt water (Pires & Prance 1985). They are between the várzea and the igapó, but did not differ species-poor and typically quite uniform. Among the between dry and rainy periods. Although Cerqueira et al. primary tree species is the mangrove, Rhizophora mangle (2016) studied only seven species in detail, two species (Figure 12). were associated with the forest type and two species to the seasonality of flooding. They identified 54 bryophyte species in 502 samples; 34 were fertile. Sexual reproduction predominated over asexual (Figure 10). Figure 9. Virola surinamensis, an igapó substrate for Figure 11. Calymperes tenerum, one of the common species bryophytes. Photo by Reinaldo Aguilar, through Creative on mangroves in eastern Thailand. Photo from Auckland Commons. Museum, through Creative Commons. Chapter 8-11: Tropics: Wet and Dry Habitats 8-11-5 Figure 13. Mangrove of Rhizophora apiculata, a favorable host for bryophytes in Thailand. Photo by Bernard Dupont, through Creative Commons. Figure 12. Rhizophora mangle, a primary species of the mangrove forest. Photo by Steve Hillebrand, through public domain. In Thailand there are about 40 tree species in the mangrove forests (Thaithong 1984). Among these, only 10 species support epiphytic bryophytes. Thaithong found Figure 14. Octoblepharum albidum, a common species in only 5 species of mosses and 21 species of leafy liverworts. the mangrove